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Description  |
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FIELD OF THE INVENTION
This invention concerns improved shotshells for use in shotguns and, more
particularly, shortened shotshells that provide firing properties
substantially equivalent to standard length shotshells.
Application Ser. No. 07/632,476 by Larry Moore entitled "Shortened
Shotshell", filed on even date herewith related is now abandoned.
BACKGROUND OF THE INVENTION
Shotshells are widely used in shotguns for hunting, law enforcement and
military combat. Since approximately the turn of the century the
dimensions of shotshells have been standardized to match one or the other
of a small number of standard barrel sizes. The internal barrel diameters
of shotguns are usually stated in terms of "gauges", as for example, 10,
12, 16, 20 and 28 gauges. The smaller the gauge number, the larger the
internal barrel diameter and the larger the shotshell diameter. The most
popular gauges today are 12 and 20 gauges.
FIG. 1A shows a simplified, partial cross-sectional and cut-away view and
FIG. 1B shows an end view of typical prior art shotshell 10. Shotshell 10
comprises metal base 12 having short metal sidewall 14 to which is
attached paper or plastic tube or sleeve 16 which makes up most of length
13, 15 of shotshell 10. Length 13 is the length of the shotshell before
sleeve 16 is crimped (i.e. rolled or folded inward to retain the powder
and shot) or after the crimp unfolds on firing. Length 15 is the length of
the crimped shotshell.
Base 12, sidewall 14 and sleeve 16 hold firing cap or primer 17, base wad
18, powder 19, compression wadding 20 and shot 22 in that order.
Generally, the larger powder charge 19, the higher metal sidewall 14 in
order to provide extra lateral (radial) strength to shotshell 10 in the
immediate vicinity of the powder explosion. End 23' of sleeve 16 is
inwardly folded to provide crimped end 23 to retain shot 22 in sleeve 16.
Sometimes with smaller size shot or when a rolled crimp is used, a thin
wad (not shown) is provided between shot 22 and crimped end 23 of sleeve
16 to insure that shot 22 is firmly retained within sleeve 16.
FIG. 2 shows a simplified, partial cross-sectional and cut-away view of
prior art shotgun potion 11 with prior art shotshell 10 in place ready for
firing. Shotgun portion 11 has chamber 27 for receiving shotshell 10.
Inner diameter 24 of shotshell 10 is about equal to inner diameter 28 of
shotgun barrel 30. Cone shaped transition zone 29 is provided between
chamber 27 and barrel 30. This is referred to in the art as a "forcing
cone". Chamber 27 is closed by breech 31 containing a firing pin indicated
by arrow 33 aligned with primer cap 17.
Inner diameter 34 of chamber 27 matches outer diameter 36 of shotshell 10
with enough clearance so that shotshell 10 may be easily inserted and
removed. Chamber 27 and breech 31 provide structural support for the
relative weak casing of shotshell 10 so as resist the radial outward force
created when powder 19 burns. When shotshell 10 is fired, compression
wadding 20 seals against inside wall 38 of shotgun barrel 30 to propel
shot 22. In this way, the full force of the rapidly expanding gases from
burning powder 19 is transferred to shot 22 and little if any gas escapes
around or through shot 22.
Most shotshells today come in one of two standard lengths, that is, 2.75
inches ("standard") and 3.0 inches ("magnum") and shotguns are chambered
to accept either the 2.75 inch standard shells or both the 2.75 inch
standard and the 3.0 inch magnum shells. A shotgun chambered for magnums
will general safely fire either standard or magnum shotshells but a
shotgun chambered for standard shotshells will not safely fire the longer
magnum shells.
The designated "length" of shotshell 10 (e.g., 2.75 inch standard or 3.0
inch magnum) refers to length 35 of chamber 27 needed to accommodate
shotshell 10 when fired, and corresponds about to overall shotshell length
13 before end 23' of sleeve 16 is crimped. Chamber length 35 must be large
enough to allow crimped end 23' of sleeve 16 to completely open out
against inner wall 39 of chamber 27 and provide a clear path for shot 22
and wad 20 to pass out of sleeve 16 and into barrel 30. If sleeve end 23
cannot fully open, then a constriction is created partially blocking
barrel entrance 29. This can lead to excessive pressure and possible
rupture of the chamber or breech.
A standard 2.75 inch shotshell has uncrimped length 13 of about 2.75 inches
and crimped length 15 of typically about 2.375-2.5 inches. When shotshell
10 is fired, crimped end 23 unfolds against wall 39 of chamber 27,
restoring the shell to approximately uncrimped length 13. Length 35 of
chamber 27 is sufficient to accommodate uncrimped shotshell length 13
between breech 31 and forcing cone entrance 29 to barrel 30, leaving at
most very small gap 25 therebetween. The close proximity of unfolded shell
end 23' and forcing cone 29 allows shot 22 and wadding 20 to pass smoothly
from sleeve 16 into barrel 30 so that the wadding can make a substantially
gas-tight seal against interior wall 38 of barrel 30.
The 2.75 inch "standard" length for shotshells dates back to the days when
such shells used black powder. Because black powder was a comparatively
weak explosive, a substantial volume of black powder was necessary to
propel the shot from the shotgun with sufficient force to be effective.
Thus, a relatively long shell casing was required to accommodate the
volume of black powder needed. The 2.75 inch shotshell length was adopted
by many gun manufacturers of that era because it was able to hold the
desired amount of black powder and they chambered their shotguns
accordingly. This became the de-facto standard that persisted long after
the use of black powder was discontinued, and still remains the standard
today. While most new guns are chambered for both 2.75 inch standard and
3.0 inch magnum shotshells, the 2.75 inch standard shotshell is still the
predominant shell type because of the very large number of existing guns
chambered for that shell length which cannot safely use the 3.0 inch
magnum shell.
Once black powder was replaced by modern smokeless power in the early
1900's, the large volume of space in the 2.75 inch standard shell length
was no longer needed for the powder charge because the smokeless powder
was much more powerful. The empty space could not be filled with smokeless
powder because that would create a grave risk of gun rupture, especially
with older guns designed for use with black powder. Whether or not any
attempt was ever made to shorten the shell casings without modifying the
gun chamber is lost in the history of gun and ammunition development near
the beginning of the present century. If such attempts were made they were
apparently unsuccessful and the standard 2.75 inch shell length was
retained and the excess space in the shell filled by additional wadding or
shot cups or other space-takers. Even today, almost a century after
smokeless powder came into widespread use, virtually all shotguns are
still manufactured to accept the 2.75 inch standard shell length in their
chambers and magazines.
Many shotguns are of the manual (pump) or semiautomatic (gas or blow-back
operated) repeating variety. Because shotshells are relatively large, they
are usually held end-to-end in tubular magazines mounted under the barrel.
Clip-type magazines where shells are held side-by-side are generally not
used with shotguns because they are too bulky.
The number of shells that a tubular magazine can accommodate is limited by
the free magazine length divided by the shell length. Some extra space is
provided in the tubular magazines to accommodate the coiled spring that
pushes the shells out of the magazine as the loading action is cycled.
Most shotgun magazines hold four 2.75 inch standard shells. An additional
round may be held in the chamber, giving a typical maximum load of five
shells. Extended magazines, which are common on military and police
shotguns, may hold five to ten shells giving a total of six to eleven
shells, but further lengthening of the tubular magazine is not desirable
because it makes the shotgun unwieldy.
While five shells may be adequate for most hunting situations, in law
enforcement and military combat there is a great premium on having as many
shells as possible in the magazine. This is because shotguns are slow and
awkward to reload in high stress, fire-fight situations. The tubular
magazine must be refilled one shell at a time. Where two opposing
combatants (e.g. police versus criminal or soldier versus soldier) are
armed with shotguns, the one with one or more extra rounds in his weapon
has a great advantage, a potentially life saving advantage.
Despite the desirability of being able to carry more shotshells in a
standard shotgun magazine, little progress has been made since the first
tubular magazine shotguns were introduced in the early part of the
century. The shotshell and magazine length of most shotgun designs have
remained virtually unchanged. If anything, newer forms of ammunition have
tended to be longer (e.g., the magnum shell) which decreases the effective
magazine capacity. Thus, a long unsatisfied need exists for shotshells
which permit a larger magazine load and which fire safely and effectively
without weapon modification.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved means and
method for shotshells of reduced length that allow at least one additional
shell to be fitted within a standard length magazine, as for example, five
shortened shells in the space of four standard prior art shells or six in
the space of five, or ten in the space of eight, etc., and which fire
safely and effectively without weapon modification, especially in
conventional existing shotguns of all types, including pump repeaters,
semi-automatic gas operated and semi-automatic blow-back operated
shotguns.
It is a further objective to provide an improved means and method for
shortened shotshells able to contain pellet and powder loads and provide
ballistic performance substantially similar to conventional prior art
standard length shotshells, despite their reduced length.
These and other objects and advantages are realized by a shortened
shotshell comprising, a shotshell casing including a base for retaining a
primer cap and a hollow tubular member extending away from the base for
retaining powder and shot, and a double-cupped wadding located between the
powder and the shot. The wadding has a first open end providing a first
cup or cavity of a first depth facing the primer for containing a majority
of the powder and a second open end providing a second cup or cavity of a
second depth facing the shot and for containing part of the shot. The
overall length of the shotshell is reduced so that at least five of the
above described shotshells fit in substantially the same length occupied
by four standard shotshells while still providing a wadding length
sufficient to prevent tilting or tumbling of the wadding between the end
of the shotshell casing and the barrel entrance and to provide a
substantially continuous gas-tight seal between the end of the shotshell
case and the barrel entrance to minimize gas blow-by. The wadding can be
made of compressed paper or of molded or machined plastic. Molded plastic
is preferred.
It is further desirable that the cavities be wider near their open ends
than near their bottoms. It is also desirable that the primer cap have an
interior end (for igniting the powder) which extends substantially to the
open end of the first cavity.
In a preferred embodiment, the wadding has a substantially cylindrical
outer shape of a predetermined diameter adapted to fit the bore of the
shotgun in which the shotshells will be used. The first cavity contains
the powder and its sidewall and the partition between it and the second
cavity must withstand the gas pressure within the shotgun chamber and
barrel without rupture.
The second cavity is intended to partly enclose one or more rows of shot
and should have a depth at least about equal the shot radius minus,
optionally, a small clearance amount depending on the wall thickness of
the second cavity. The purpose of the second cavity is to add length to
the outer wall of the wadding so that it can bridge the gap between the
end of the shotshell casing and the barrel without permitting any
significant gas blow-by, that is, the outer wall of the wadding should be
long enough so that its forward end (formed by the wall of the second cup
partly around the shot) enters the barrel while the aft end (formed by the
wall of the first cup around the powder) is still within the shell casing.
In this way, a continuous substantially gas-tight seal is maintained and
gas blow-by is substantially prevented without depending on radial
expansion of the wadding to contact the interior wall of the gun chamber.
In a preferred embodiment, the wadding has an overall length of about at
least about 0.495 to 0.625 inches plus the radius of the shot intended to
be used, less a small (e.g. 0.005-0.01 inch) clearance amount, typically
at least about 0.625 inches. For example, "00-buckshot", which is commonly
used in police and military loads, has a radius of about 0.165 inches,
giving an overall wadding length of about 0.65 inches. Longer waddings
obtained by means of deeper second cavities can also be used provided
there is sufficient radial clearance within the shotshell casing to
accommodate both the wall of the second cavity and the shot. Where there
is not sufficient radial clearance within the shell casing, it is
preferable to have the depth of the second cavity be less than the shot
radius.
The first cavity depth is usefully about 0.25-0.5 inches, preferably about
0.35 to 0.4 inches and typically about 0.35 inches. The partition between
the two cavities is preferably about 0.1 to 0.2 inches, typically about
0.15 inches thick. The outer diameter of the wadding is chosen so that it
can fit within the hull of the shotshell and engage the shotgun bore for
which the shells are intended, and will vary with the bore size and
shotshell diameter. For a 12 gauge shotshell, the wadding has a diameter
preferably in the range 0.725 to 0.735 inches, typically about 0.73
inches.
It is further desirable that the wadding cavities have tapered sidewalls
whose thicknesses increase toward the bottoms of the cavities. This
facilitates radial distension of the end portion of the first sidewall
near the first open end when the shotshell is fired so that it seals
tightly against the inner wall of the shell casing and shotgun barrel
without rupture. The tapered second sidewall allows it to extend into the
otherwise empty space between the first row of shot and the inner wall of
the shotshell casing created by the curvature of the shot. Further, the
sidewall tapers provide a greater sidewall thickness where they meet the
closed portion of the wadding which separates the two cavities, thereby
increasing the wadding strength to avoid rupture. A taper angle of 5-15
degrees and a sidewall skirt thickness at the end of the first cavity of
about 0.01-0.02 inches is suitable. A sidewall rim thickness at the end of
the second cavity of about 0.005 inches or more is suitable.
The above described shortened shotshell is made by a method comprising,
providing a shotshell case having a base and an open end and a length
between the base and open end such that, after closure of the open end,
five shortened shotshells fit in the same length occupied by four standard
shotshells, then introducing into the shotshell casing a wadding having
therein back-to-back cavities separated by a solid partition where a first
cavity faces the base for substantially containing most of the shotshell
powder and a second cavity, for example, about one shot radius deep faces
the shot, introducing the shot into the casing between the wadding and the
open end so that the forward rim of the wadding around the second cavity
extends between part of at least the first row of shot and the interior
casing wall, and closing the open end of the casing to retain the shot. It
is desirable that the step of introducing the wadding include introducing
a substantially cylindrical wadding having a predetermined length and
diameter as explained above.
It further desirable that the step of providing the casing include
providing a casing having a primer cap extending into the casing with an
end interior to the casing for igniting the powder, and that the step of
providing the wadding comprises inserting the wadding into the casing
until the interior end of the primer cap extends substantially to the
first opening in the wadding.
By placing the powder inside the wadding and having the first end of the
wadding extend deep into the base of the shell near the primer firing hole
and by having the second end of the wadding extend at least into the space
around the first row of shot created by the shot curvature, a long wadding
is obtained despite the reduced shell length and without any significant
reduction in the shot or powder load.
Having a long wadding is important. It maintains a smooth transition from
shotshell sleeve to barrel entrance despite the increased separation that
arises from shortening the shotshell. Unless the wadding is long enough to
bridge this gap gas blow-by can occur, adversely affecting the shot
pattern and muzzle velocity. With the present invention a near perfect gas
seal is maintained, tilting and tumbling of the wadding is avoided and the
shot pattern and muzzle velocity of the shortened shotshell are
substantially the same as the standard shotshell for the same shot and
powder loads. Further, the shotshell employing the double-cupped wadding
fires satisfactorily in a greater variety of weapons, including blow-back
operated auto-loaders, providing more reliable auto-loading. These are
important features and advantages of the invented design.
As used herein the word "shotshell" is intended to refer to a cartridge
containing powder, wadding, and shot, slug or projectile of any kind, for
use in a shotgun or other firearm. The word "wadding" is intended to refer
to a device, made of any material (e.g., cloth, paper, plastic and
combinations thereof), located between the powder and shot of a shotshell
for sealing against the interior of a shotgun barrel when the shotshell is
fired so as to prevent substantial gas leakage past the wadding. The word
"wad" is used generally to refer to any spacer or padding or the like that
may be located anywhere within the shotshell casing, e.g., at the base end
between the base and the powder or at the shot end to retain the shot or
elsewhere. As used herein the word "round" in the context of a cartridge,
shell or bullet is intended to refer to a shotshell. The foregoing
definitions are intended to apply to these words in singular or plural
form.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A shows a simplified cross-sectional and partially cut-away view and
FIG. 1B shows an end view of a typical shotshell according to the prior
art;
FIG. 2 shows a simplified cross-sectional and partially cutaway view of the
shotshell of FIGS. 1A-B installed in the chamber of a typical prior art
shotgun;
FIG. 3A shows a simplified cross-sectional and partially cut-away view of a
shortened shotshell according to the present invention, and FIGS. 3B-D
show enlarged portions thereof according to different embodiments of the
present invention;
FIG. 4 shows a simplified cross-sectional and partially cutaway view of the
shotshell or FIG. 3 installed and ready for firing in the same prior art
shotgun as illustrated in FIG. 2;
FIG. 5 shows a simplified cross-sectional view of an improved wadding and
FIGS. 6-7 show opposed end views of the wadding of FIG. 5;
FIG. 8 shows a simplified cross-sectional view and FIGS. 9-10 show opposed
end views similar to FIGS. 5-7 but of a further improved wadding according
to a further embodiment of the present invention; and
FIG. 11 shows a simplified cross-sectional view similar to FIG. 8 but
according to a still further embodiment of the present invention..
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A standard shotgun magazine intended to hold four 2.75 inch standard
shotshells has a clearance space of about ten inches. This clearance space
allows for some variation in the typical 2.375-2.5 inch crimped length of
the standard 2.75 inch shotshell. In order to accommodate five shortened
shells in the same space, each shortened shell should be about 10/5=2.0
inches. To accommodate reasonable manufacturing variation, the crimped
length of a shortened shotshell should be typically in the range of
1.9-2.0 inches and preferably not much over 2.0 inches.
A standard shotshell can be shortened by making the internal waddings or
other space-takers shorter or by decreasing the powder and/or shot load or
both. For example, if the total length of wadding in the shell (measured
along the direction of fire) is reduced by approximately 0.375-0.5 inch,
then the overall shell casing length can be reduced by about the same
amount to give the desired 1.9-2.0 inch shell length (crimped). Shells
made in this manner have the desired length but poor ballistic properties.
Tests showed that reduced length shells made with shortened wadding had
highly variable muzzle velocity (e.g., up to 25% variation) and erratic
shot patterns. This was true even though substantially the same powder and
shot loads were used as for conventional length shells.
It was determined that the degradation in ballistic properties of these
reduced length shells employing shortened waddings is due to gas blow-by
and tilting or tumbling of the short wadding during the brief time when
the short wadding is the gap between the unfolded end of the shortened
shell casing and the barrel entrance. With a shortened shell (e.g., 2.0
inch crimped, 2.375 inch uncrimped length), there is a gap of at least
0.375 inches between the end of the unfolded shell casing and the barrel
entrance in a gun chambered for conventional 2.75 inch length shells and
0.875 inches in a gun chambered for 3.0 inch shells. When the short
wadding is in this gap, the wadding is unconstrained by either the sleeve,
chamber or barrel walls and there is nothing to prevent gas blow-by around
the wadding. The turbulent gas blow-by causes the wadding to tilt or
tumble.
Prior art waddings fired from shortened shells were carefully examined and
found to have scuff marks created when the wadding entered the barrel
slightly tilted or off center. Such scuff marks are not observed with
conventional standard length shells because gap 25 (see FIG. 2) between
the end of the standard shotshell sleeve and the barrel entrance is small
compared to the standard wadding length and the forward end of the wadding
begins to enter the barrel before the following end of the wadding has
exited the sleeve. This prevents blow-by and tilting or tumbling of the
wadding from the conventional shotshell. With reduced length shotshells
and correspondingly shortened prior art waddings, this smooth transition
is not possible and poor ballistic performance results.
It was discovered that the foregoing and other problems are avoided and
reduced length shotshells of excellent ballistic performance obtained if
the interior construction of the shotshell is changed so that a long
wadding is provided while still maintaining space for about the same
powder and shot load. This was accomplished by making the wadding hollow,
that is, with a double-cup shape, with the open end of the first cup
facing the primer for substantially containing the powder and an open of
the second cup facing and at least partially containing the shot.
FIG. 3A shows a simplified cross-sectional and partially cut-away view of
shortened shotshell 40 according to the present invention and with FIGS.
3B-D showing enlarged portion according to different embodiments. FIG. 4
shows the same shotshell 40 installed and ready for firing in conventional
shotgun portion 11, the same as in FIG. 2. FIG. 5 shows a simplified
cross-sectional view of the wadding of the present invention in greater
detail, FIG. 6 shows a view of the end of the wadding which faces the
primer and FIG. 7 shows a view of the end of the wadding which faces the
shot, according to a first embodiment. FIGS. 8-10 are similar to FIGS.
5-7. but according to a further embodiment and FIG. 11 shows a still
further embodiment.
Referring now to FIGS. 3a-4, improved shotshell 10 comprises base 42 with
sidewall 44 and sleeve 46 analogous to prior art shotshell 10, but with
shortened overall length 43 and crimped length 45. Overall (uncrimped)
length 43 is, typically, about 2.375 inches and crimped length 45 is
typically about 1.9-2.0 inches.
The maximum crimped length 43 is determined by the desire to fit at least
one extra shell into a standard magazine length, e.g., five rounds in a
conventional four round magazine, six rounds in a five round magazine, ten
rounds in an eight round magazine, and do forth. As has been explained
above, this leads to a crimped length of about two inches for most guns.
Based on the description herein, those of skill in the art will understand
how to choose the length of a crimped round, and from that determine the
length of the same round when uncrimped, depending on the amount of crimp
needed to retain the shot. The larger the shot, the less crimp is needed.
The larger the gauge, the more crimp that can be used, i.e., the greater
the shell diameter, the more sleeve length that can be folded in to close
the end of the shell. For simplicity of manufacture, it is desirable to
use a single uncrimped shell length suitable for obtaining the desired
1.9-2.0 inch crimped length for each gauge even though different size shot
may be inserted therein. For 12 gauge shortened shells, an uncrimped shell
length of about 2.375 inch is preferred.
Shotshell 40 has therein firing primer 47, base wad 48, powder 49, wadding
50 and shot 52 in that order. Sleeve 46 has rolled or crimped end 53
analogous to end 23 of shotshell 10. Shotshell 40 has outer sleeve
diameter 54 and inner diameter 66 substantially the same as diameters 36,
24 respectively, of prior art shotshell 10. The parts and dimensions of
shotgun portion 11 of FIG. 4 are the same as in FIG. 2 and the same
reference numbers are used in FIG. 4. However, due to the smaller length
43, 45 of shortened shell 40, much larger gap 55 now exists between
unfolded end 53 of sleeve 46 of shotshell 40 and forcing cone 29 at the
entrance to barrel 30 of shotgun 11.
Referring now to FIGS. 3B and 5-7, wadding 50 is, in the preferred
embodiment, of substantially cylindrical outer shape of diameter 60 and
length 62. Wadding 50 has end 64 facing toward powder 49 and end 66 facing
toward shot 52. End face 64 of wadding 50 has opening 67 forming cavity 68
therein of depth 70 and diameter 72 near end face 64. Sidewall 74
separates cavity 68 from the substantially cylindrical outer surface 71 of
wadding 50.
It is desirable that sidewall 74 be tapered so as to have thickness 76 near
end face 64 and thickness 78 near cavity bottom 80. Wadding end portion 86
of thickness 82 separates cavity bottom 80 from end face 66. Sidewall 74
has taper angle 84.
For a twelve gauge shotgun shell, wadding diameter 60 is preferably about
0.725-0.735 inches, typically about 0.73 inches, wadding length 62
preferably about 0.495-0.625, typically about 0.5 inches, thickness 82 of
end portion 86 preferably about 0.1-0.2 inches, typically about 0.15
inches, thickness 76 of sidewall 74 at open end face 64 preferably about
0.01-0.03 inches, typically about 0.02 inches, cavity depth 70 usefully
about 0.25 to 0.5 inches, preferably about 0.30-0.45 inches, typically
about 0.35 inches, and taper angle 84 preferably about 5-15 degrees,
typically about 10 degrees. It is desirable that cavity sidewall 74 be
thicker where it intersects end portion 86 and that intersection 88 of
cavity bottom 80 and interior cavity wall 90 be chamfered or rounded.
It is important that the wadding not rupture when the shell is fired,
otherwise gas leakage results. Thus, sidewall 74 and end portion 86 should
be thick enough and strongly joined enough to resist the force of the
gases generated by burning powder 49. The tapered sidewall which is
thicker at the bottom of the cavity than at the open end, and the
chamfered or rounded intersection between the cavity bottom and interior
wall, each contribute to preventing wadding 50 from rupturing during
firing.
Tapered sidewall 74 has a further advantage of permitting end 64 of wadding
50 to expand radially, that is by increase in diameter 72, so that the
portion of exterior wadding surface 71 near end 64 can make a gas-tight
seal against the interior wall of shell casing 46 and interior wall 38 of
barrel 30. To the extent that end 64 of wadding 50 can expand without
rupture into larger diameter 34 of chamber 27 in gap 55 once it leaves
sleeve 46 and before it enters forcing cone 29 and barrel 30, gas blow-by
in gap 55 is reduced. Having sidewall 74 taper to a comparatively thin
edge width 76 at end 64 facilitates this. Inspection of wadding 50 after
firing from shortened shotshells 40 showed that end 64 of wadding 50 had
expanded radially to a bell-like shape, i.e., diameter 72 had increased
while diameter 60 remained substantially unchanged, and without rupture of
the wadding. This indicates that wadding 50 is expanding radially to
provide at least some sealing action against inner wall 39 of chamber 27
in gap 55.
The wadding can be made of compressed paper or of molded or machined
plastic. Materials used for conventional prior art molded plastic waddings
are suitable provided that they are not too hard or rigid. Molded high
density polyethylene is preferred. It is desirable that the skirt of the
wadding adjacent the cavity opening be sufficiently elastic to expand into
chamber 27 and/or forcing cone 29 without rupture so as to improve gas
sealing.
Tests made on twelve gauge shortened shotshells of the above described
construction and dimensions, and of a length that allowed five to fit in
the space of four or six in the space of five, etc., gave excellent
performance compared to standard shells with conventional powder and shot
loads, that is, substantially similar muzzle velocity and shot patterns.
The ballistic performance of the shortened shotshell is substantially the
same as an equivalently loaded standard 2.75 inch shell.
Shortened shotshell 40 is made by a method comprising, providing shotshell
case 44, 46 having base 42 and open end 53' and length 45 between base 42
and open end 53' such that, after folding in end 53' to provide crimped
end 53, five shortened shotshells 40 fit in the same length occupied by
four closed standard shotshells 10, then introducing into shotshell casing
44, 46 wadding 50 having therein opening 67 forming cavity 68 facing base
42 for substantially containing most of shotshell powder 49, introducing
shot 52 into casing 44, 46 between wadding 50 and open end 53', and
forming crimped end 53 to retain shot 52. It is desirable that the step of
introducing wadding 50 include introducing substantially cylindrical
wadding 50 having predetermined length 62 and diameter 60, wherein
diameter 60 is chosen so as to closely engage bore 38 of shotgun 11 for
which shells 40 are intended, and wherein length 62, cavity depth 70, end
wall thickness 82, sidewall thickness 76 and taper angle 84 have the
magnitudes previously described.
It further desirable that the step of providing the casing include
providing casing 44, 46 having primer cap 47 extending into base 42 and
casing 44, 46 with an end interior to casing 44, 46 for igniting powder
49, and that the step of providing wadding 50 comprises inserting wadding
50 into casing 44, 46 until the interior end of primer cap 47 extends
substantially to opening 67 of wadding 50.
The above-described shortened shotshell of the present invention having the
wadding design illustrated in FIGS. 5-7 was tested successfully in a
variety of shotguns, as for examples, the models 870 and 1100 manufactured
by the Remington Arms Company of Ilion, N.Y., the model 1200 manufactured
by the Winchester Arms Company of Hew Haven, Conn., and the model 37
manufactured by the Ithaca Arms Company of Ithaca, N.Y. and others.
Difficulties were encountered with the shotshell and wadding design of
FIGS. 5-7 in only two gun models, the model 500 manufactured by the
Mossberg Arms Company of Northhaven, Conn. and the model Super 90
manufactured by the Benelli Arms Company of Urbino, Italy. With the first,
the shortened shells did not transfer properly from the magazine to the
chamber because their reduced length permitted them to fall through a slot
in the loading mechanism of that gun model. In the second, the reduced
length shells sometimes failed to eject properly. The Benelli Super 90
utilizes a blow-back operated auto-loading mechanism, whereas the other
auto-loaders tested are all of the gas operated variety. These were the
only difficulties encountered in a large number of firing tests with many
different guns.
It was further discovered that the failure to consistently eject in
blow-back operated auto-loaders, such as for example, the Benelli Super
90, could be overcome by the wadding design illustrated in FIGS. 3C-D and
8-11.
The wadding of FIGS. 3C-D and 8-11 differs from the wadding of FIGS. 3B and
5-7 in that it has a second opening 92, 92' forming second cavity 94, 94'
of depth 96, 96' in end face 66. Rim portion 98, 98' of cavity 94, 94' is
curved or angled so as to fit up around shot 52. Rim portion 98 desirably
has a radius of curvature 97 about equal to radius of curvature 99 of shot
52.
While rim portion 98, 98' is shown as being curved, which arrangement is
preferred, it may consist of one or more conical segments. The exact shape
of rim portion 98 may vary so long as it extends into the otherwise empty
space left between the first row of spherical shot closest to face 100 of
wadding 50' and the inner wall of sleeve 46 in which wadding 50' and shot
52 are inserted. This small annular space has an inward facing curvature
determined by the radius of curvature of the shot and an outer perimeter
determined by the diameter of the inner cylindrical wall of sleeve 46. By
utilizing this otherwise empty space, the length of wadding 50' is
increased by amount 96 without any increase in the length of shotshell 40
or decrease in shot or powder load. This additional length helps insure
that end 106 of wadding 50' begins to seat against barrel entrance 29
before end 64 of wadding 50 leaves sleeve 46 of reduced length shotshell
40. This minimizes the possibility of gas blow-by and pressure loss when
wadding 50 is transiting gap 55. This leads to more consistent shell
ejection and reload cycling in blow-back operated semi-automatic shotguns,
which are apparently more sensitive to slight gas leaks than are gas
operated auto-loaders.
For the wadding depicted in FIGS. 3C 8-10 sized for use in a twelve gauge
shell, dimensions 60, 62, 70, 72, 76, 82 and 84 are similar to those
described for the embodiment shown in connection with FIGS. 5-7. Overall
wadding length 63 is equal to length 62 of first cavity 68 and partition
86, plus depth 96 of second cavity 94. Depth 96 is preferably at least
equal to radius 99 of shot 52. "OO-buckshot" for example, has a radius of
0.165 inches, but larger or smaller shot may also be used. While rim 106
of wadding 50', i.e., the skirt of cavity 94, is shown as tapering to a
knife edge, it desirably has a small radial thickness parallel to diameter
60 of about 0.003-0.01 inches, typically about 0.005 inches. This is
desirable to avoid crumpling of rim 106 of wadding 50' when it encounters
barrel entrance 29.
FIGS. 3D and 11 are simplified cross-sectional views through wadding 50"
according to a further embodiment of the present invention. The end views
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